See the link below for such a mechanism that is apparently malfunctioned in your source text.

http://www.mobilitycontrols.co.uk/product.php/384/automatic_...

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Note added at 10 hrs (2014-02-20 23:40:46 GMT)
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I believe it's the best option for you because you can see my suggestion from the English link I provided as proof. Others don't have proof.

For your understanding, Egmont, I can give you more explanations as follows:

直接 ＝ automatic ＝no need to open it via any other channels （e.g. your key or hand).

弹开 = opening 弹开; it usually means the object is open mechanically, not by hand. Of course it is not open like a bullet if you read it with common sense although 弹 is part of 子弹 which means 'bullet'. But when used as a single word, it means something else. For example, would you say the English word 'bulletin' means 'a bullet inside'? :)